Wireless communication terminal device and control channel forming method

ABSTRACT

Provided are a wireless communication terminal device and a control channel forming method with which, in the forming of a control channel for transmitting control information including an ACK/NACK and CSI (channel state information), wasteful use of resources is reduced compared to that in related art. In the case where CSI is transmitted independently, and in the case where CSI and an ACK/NACK are transmitted at the same time, the same format is used to form a control channel. Furthermore, in the case where an ACK/NACK is transmitted independently, another format is used if a component carrier (CC) number is equal to or less than 2, and the same format is used if the CC number is equal to or greater than 3.

TECHNICAL FIELD

The present invention relates to a radio communication terminalapparatus and a control channel formation method in a mobilecommunication system that transmits control information through achannel used on an uplink.

BACKGROUND ART

3GPP (3rd Generation Partnership Project) has standardized LTE (LongTerm Evolution) and LTE-Advanced, and is currently proceeding with thestandardization for further enhancement in order to achieve high-speedand high-capacity communication between a radio communication basestation apparatus (hereinafter abbreviated as “base station”) and aradio communication terminal apparatus (hereinafter abbreviated as“terminal”).

LTE and LTE-Advanced adopt OFDMA (Orthogonal Frequency Division MultipleAccess) as a downlink communication scheme and SC-FDMA (Single CarrierFrequency Division Multiple Access) as an uplink communication scheme.

Channels and signals used on an uplink include, for example, PUSCH(Physical Uplink Shared Channel) and PUCCH (Physical Uplink ControlChannel). PUSCH is a channel for transmitting a data signal. PUCCH is achannel for transmitting control information such as ACK/NACK or CSI(Channel State Information).

ACK/NACK is information indicating an error detection result of downlinkdata of each transport block (TB) transmitted from a base station and is1-bit information indicating either ACK (no error) or NACK (error).

CSI is information indicating a measurement result of downlink channelquality. CSI includes CQI (Channel Quality Indicator), PMI (PrecodingMatrix Indicator) and RI (Rank Indicator).

Here, LTE-Advanced Release 10 (hereinafter described as “Rel.10”)supports carrier aggregation (CA) that operates a plurality of unitcarriers (component carriers, hereinafter called “CCs”) based on theunit of a frequency bandwidth of a maximum of 20 MHz (that is, maximumfrequency bandwidth in LTE) bundled together in order to supportwideband transmission (e.g., see NPLs 1, 2 and 3). In CA, one PCC(Primary Component Carrier) and one or more SCCs (Secondary ComponentCarriers) are configured. The 3GPP specification may describe CC as acell, PCC as a PCell (Primary Cell), and SCC as an SCell (SecondaryCell). When a plurality of CCs are used on an uplink, PUCCH istransmitted by only PCC so as not to increase PAPR (Peak to AveragePower Ratio).

In Rel.10, it is possible to use different PUCCH transmission formatsaccording to the number of downlink CCs (hereinafter, simply describedas “the number of CCs”) supported by a terminal, that is, the number ofACK/NACKs fed back by the terminal. More specifically, when the numberof CCs is 1, the terminal uses format 1 a/1 b to feed back ACK/NACK to abase station. When the number of CCs is 2, the terminal uses channelselection using format 1 b to feed back ACK/NACK to the base station. Onthe other hand, when the number of ACK/NACKs is 3 or more, the terminaluses format 3 to feed back ACK/NACKs to the base station.

Rel.10 defines two types of CSI feedback method: periodic CSI andaperiodic CSI. With aperiodic CSI, the terminal feeds back CSI only onceat timing instructed by the base station. With periodic CSI, theterminal feeds back CSI to the base station using format 2 at reportingcycles (e.g., 5 ms, 10 ms) configured for each terminal.

Format 1 a/1 b is a transmission format in which a channel is dividedinto Ncs×Noc⁽¹⁾ portions within one RB with Ncs cyclic shifts and Noc⁽¹⁾OCC sequences. Note that signal points of BPSK are used for format 1 aand signal points of QPSK are used for format 1 b. Format 2 is atransmission format in which a channel is divided by Ncs cyclic shiftswithin one RB. Format 3 is a transmission format in which a channel isdivided into Noc⁽³⁾ portions within one RB. Note that Ncs=12, Noc⁽¹⁾=3,and Noc⁽³⁾=4 or 5.

The transmission capacity of format 1 a is 1 bit. The transmissioncapacity of format 1 b is 2 bits. The transmission capacity of channelselection using format 1 b is 4 bits. The transmission capacity offormat 2 is 13 bits. The transmission capacity of format 3 is 21 bits.

Resources (transmission capacity) for the terminal to transmit ACK/NACKand periodic CSI are reserved. The resources reserved for periodic CSIare indicated from the base station to the terminal by RRC signalingsemi-statically.

In Rel.10, when ACK/NACK and periodic CSI are assigned to the samesubframe, ACK/NACK is given priority over periodic CSI and periodic CSIis dropped (not transmitted). However, if periodic CSI is droppedfrequently, the measurement accuracy of downlink channel qualitydeteriorates.

Thus, in Release 11 (hereinafter described as “Rel.11”), which isLTE-Advanced, studies are being carried out on the possibility ofsupporting multiplexed transmission of ACK/NACK and periodic CSI whentransmission subframes of ACK/NACK and periodic CSI overlap (e.g., NPL4).

NPL 4 describes that format 3 is used when ACK/NACK and periodic CSI(hereinafter described as “CSI”) are simultaneously transmitted, and aPUCCH transmission format of Rel.10 is used otherwise, that is, whenACK/NACK or CSI is singly transmitted. That is, ACK/NACK is transmittedin format 1 b when the number of CCs is 1 or 2 and transmitted in format3 when the number of CCs is 3 or more. CSI is transmitted in format 2.

CITATION LIST Non-Patent Literature

NPL 1

3GPP TS 36.211 V10.3.0, “Physical Channels and Modulation (Release 10),”September, 2011

NPL 2

3GPP TS 36.212 V10.3.0, “Multiplexing and channel coding (Release 10),”September 2011

NPL 3

3GPP TS 36.213 V10.3.0, “Physical layer procedures (Release 10),”September 2011

NPL 4

3GPP TSG RAN WG1 meeting, R1-113778 (November 2011)

SUMMARY OF INVENTION Technical Problem

Whether or not downlink data is transmitted is determined by schedulingin units of subframes by the base station and this is transmitted in thefourth subframe from (that is, 4 ms after) a subframe in which downlinkdata is received. For this reason, the terminal cannot know timing oftransmitting ACK/NACK beforehand.

According to the method described in NPL 4, the terminal needs toreserve resources of both format 2 and format 3 in order to be preparedfor CSI single transmission and for simultaneous transmission withACK/NACK at the transmission timing of CSI.

Therefore, according to the method described in NPL 4, when ACK/NACK andCSI are simultaneously transmitted, the reserved format 2 resourcesbecome vacant, and when CSI is singly transmitted, the reserved format 3resources become vacant. Thus, according to the method described in NPL4, more resources are wasted.

An object of the present invention is to reduce such waste of resources.

Solution to Problem

A radio communication terminal apparatus according to an aspect of thepresent invention includes: a formation section that forms a controlchannel for transmitting control information including at least one ofACK/NACK and CSI (Channel State Information), using one of a pluralityof formats; and a transmitting section that transmits the formed controlchannel, in which the formation section uses a first format when thecontrol information includes only the CSI out of the ACK/NACK and theCSI, and when the control information includes the ACK/NACK and the CSI.

A control channel formation method according to an aspect of the presentinvention is a method for forming a control channel for transmittingcontrol information including at least one of ACK/NACK and CSI (ChannelState Information), using one of a plurality of formats, the methodincluding forming the control channel using a first format when thecontrol information includes only the CSI out of the ACK/NACK and theCSI, and when the control information includes the ACK/NACK and the CSI.

Advantageous Effects of Invention

According to the present invention, it is possible to reduce waste ofresources in mapping of ACK/NACK and CSI compared to the related art.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating a configuration of a terminalaccording to Embodiment 1 of the present invention;

FIG. 2 is a block diagram illustrating a configuration of a base stationaccording to Embodiment 1 of the present invention;

FIG. 3 illustrates an example of Embodiment 1 of the present invention;

FIG. 4 illustrates an example of Embodiment 1 of the present invention;

FIG. 5 illustrates an example of a conventional method;

FIG. 6 illustrates an example of a conventional method;

FIG. 7 illustrates an example of Embodiment 2 of the present invention;

FIG. 8 illustrates an example of Embodiment 2 of the present invention;

FIG. 9 illustrates an example of Embodiment 3 of the present invention;

FIG. 10 illustrates an example of Embodiment 3 of the present invention;

FIG. 11 illustrates an example of Embodiment 4 of the present invention;and

FIG. 12 illustrates an example of a configuration of resources for CSIof Embodiment 4 of the present invention.

DESCRIPTION OF EMBODIMENTS

Hereinafter, each embodiment of the present invention will be describedin detail with reference to the accompanying drawings. Hereinafter, anFDD (Frequency Division Duplex) system will be described as an example.

Embodiment 1 [Configuration of Terminal]

FIG. 1 is a block diagram illustrating a configuration of a terminalaccording to Embodiment 1 of the present invention. Terminal 100 shownin FIG. 1 is mainly configured of receiving section 101, FFT section102, demodulation section 103, decoding section 104, channel qualitymeasuring section 105, ACK/NACK generating section 106, CSI generatingsection 107, multiplexing section 108, control channel formation section109, DFT-S-OFDM signal generating section 110 and transmitting section111.

Receiving section 101 performs RF processing such as down-conversion orAD conversion on a radio signal transmitted from base station 200 (seeFIG. 2) and received via an antenna, and obtains a baseband OFDM signal.

FFT section 102 performs FFT processing on the OFDM signal outputtedfrom receiving section 101 to thereby transform the signal into afrequency domain signal. Demodulation section 103 performs demodulationprocessing on the signal outputted from FFT section 102 and extractsdata. Decoding section 104 performs error correction processing such asturbo decoding and error detection processing such as CRC detection onthe data outputted from demodulation section 103.

Channel quality measuring section 105 measures channel quality using areference signal included in the output signal of FFT section 102. Thechannel quality includes rank of propagation path, information ondirectivity (that is, precoding method on the transmitting side receivedwith high receiving quality), receiving power and receiving quality suchas SIR and SINR.

ACK/NACK generating section 106 generates ACK/NACK based on the errordetection result of decoding section 104. More specifically, ACK/NACKgenerating section 106 generates ACK when no error is detected andgenerates NACK when an error is detected.

CSI generating section 107 generates CQI, PMI and RI from the channelquality measured by channel quality measuring section 105 and generatesCSI by integrating the information.

When CSI and ACK/NACK are transmitted in the same subframe, multiplexingsection 108 multiplexes the ACK/NACK outputted from ACK/NACK generatingsection 106 and the CSI outputted from CSI generating section 107. As anexample of the multiplexing method, a method is used whereby CSI andACK/NACK are encoded (e.g., Reed Muller coding or convolutional coding)respectively, and then interleaved to generate a transmission bitstring. Note that cycles (timings) of subframes in which CSI istransmitted are configured beforehand. A subframe in which ACK/NACK istransmitted is the fourth subframe from the subframe in which downlinkdata is received.

Control channel formation section 109 reserves a predetermined PUCCHtransmission resource and forms PUCCH for transmitting controlinformation including ACK/NACK and/or CSI in accordance with each of thecases of ACK/NACK single transmission, CSI single transmission andACK/NACK and CSI simultaneous transmission using predetermined formats.Details of the processing carried out by control channel formationsection 109 will be described later.

DFT-S-OFDM signal generating section 110 performs DFT, mapping tosubcarriers and IFFT processing on (not shown) PUSCH (data signal) andPUCCH (control information) outputted from control channel formationsection 109 to thereby generate a time domain DFT-S-OFDM signal.

Transmitting section 111 performs RF processing such as D/A conversionor up-conversion on the DFT-S-OFDM signal outputted from DFT-S-OFDMsignal generating section 110 and transmits a radio signal to basestation 200 via an antenna.

[Configuration of Base Station]

FIG. 2 is a block diagram illustrating a configuration of a base stationaccording to Embodiment 1 of the present invention. Base station 200shown in FIG. 2 is mainly configured of receiving section 201, FFTsection 202, control channel extraction section 203, ACK/NACKdemodulation section 204, CSI decoding section 205, scheduling section206, coding section 207, modulation section 208, mapping section 209,IFFT section 210, and transmitting section 211.

Receiving section 201 performs RF processing such as down-conversion orAD conversion on a radio signal transmitted from terminal 100 andreceived via an antenna and obtains a baseband DFT-S-OFDM signal.

FFT section 202 performs FFT processing on the DFT-S-OFDM signaloutputted from receiving section 201 to thereby transform the DFT-S-OFDMsignal into a frequency domain signal. Control channel extractionsection 203 extracts PUCCH (control information) from the signaloutputted from FFT section 202 and further divides the information intoan ACK/NACK signal and a CSI signal.

ACK/NACK demodulation section 204 performs decoding processing on theACK/NACK signal outputted from control channel extraction section 203and extracts ACK/NACK. CSI decoding section 205 performs decodingprocessing on the CSI signal outputted from control channel extractionsection 203 and extracts CSI.

Scheduling section 206 performs scheduling based on the ACK/NACK and CSItransmitted from each terminal and outputs the next data to betransmitted.

Coding section 207 performs coding processing such as turbo coding onthe data outputted from scheduling section 206. Modulation section 208performs modulation processing such as QPSK on the data outputted fromcoding section 207. Mapping section 209 maps the signal outputted frommodulation section 208 to an RB.

IFFT section 210 performs IFFT processing on the signal outputted frommapping section 209 to thereby generate a time domain OFDM signal.

Transmitting section 211 performs RF processing such as D/A conversionor up-conversion on the OFDM signal outputted from IFFT section 210 andtransmits a radio signal to terminal 100 via an antenna.

Next, a control channel formation method by terminal 100 according tothe present embodiment will be described. FIG. 3 illustrates an exampleof the present embodiment when the number of CCs is 2 or less. FIG. 4illustrates an example of the present embodiment when the number of CCsis 3 or more. Note that in FIG. 3 and FIG. 4, white regions illustrateresources that are reserved but not used. A/N indicates ACK/NACK.

The present embodiment uses format 3 (same transmission format) for whensingly transmitting CSI and for when CSI and ACK/NACK are simultaneouslytransmitted (hereinafter, “simultaneously transmitted” includes“multiplexed and transmitted”) as well. When ACK/NACK is singlytransmitted, the present embodiment uses format 1 b if the number of CCsis 2 or less and uses format 3 if the number of CCs is 3 or more.

For this reason, when the number of CCs is 2 or less as shown in FIG. 3,the terminal always (in every subframe) reserves resources of format 1 band at the same time reserves resources of format 3 at transmissiontiming of CSI. On the other hand, when the number of CCs is 3 or more asshown in FIG. 4, the terminal always reserves resources of format 3.

FIG. 5 illustrates an example of a conventional method when the numberof CCs is 2 or less. FIG. 6 illustrates an example of a conventionalmethod when the number of CCs is 3 or more. In FIG. 5 and FIG. 6, whiteregions indicate resources reserved but not used. A/N indicatesACK/NACK.

Since the conventional method uses format 2 when singly transmitting CSIas shown in FIG. 5 and FIG. 6, reserved format 2 resources may be vacantif ACK/NACK and CSI are simultaneously transmitted, whereas when CSI issingly transmitted, reserved format 3 resources may be vacant. As shownabove, according to the conventional method, more resources are unusedand wasted.

In contrast, when the number of CCs is 2 or less, the present embodimentuses format 3 for both when singly transmitting CSI and whensimultaneously transmitting ACK/NACK and CSI as shown in FIG. 3, and thepresent embodiment uses format 1 b when ACK/NACK is singly transmitted.This eliminates the necessity for reserving format 2 resources, and canthereby reduce waste of resources compared to the related art.

Here, when the number of CCs is 2 or less, and when only CSI istransmitted, the present embodiment uses excessive resources by anamount corresponding to the difference in resource sizes between format3 and format 2, but since CSI is periodically generated, the resourceamount of CSI is smaller than the resource amount of all subframes. Onthe other hand, ACK/NACK may be generated in every subframe, andtherefore the present embodiment uses format 1 b having a small resourcesize for transmission of ACK/NACK. This makes it possible to reducewaste of resources when simultaneously transmitting ACK/NACK and CSIcompared to waste of resources when not simultaneously transmittingACK/NACK and CSI.

When the number of CCs is 3 or more, the present embodiment transmitsACK/NACK and CSI in format 3 in both cases as shown in FIG. 4. Thiseliminates the necessity for reserving format 2 resources, and canthereby reduce waste of resources compared to the related art.

Embodiment 2

CSI may include one of CQI, PMI and RI, or two of CQI, PMI and RI or allthree of CQI, PMI and RI. RI is information of 1 or 2 bits, and CQI andPMI are information of 5 to 10 bits. A transmission cycle of RI islonger than that of CQI or PMI. For example, the transmission cycle ofRI is 60 ms and the transmission cycle of CQI or PMI is 10 ms.

In view of the above-described aspects, Embodiment 2 controlstransmission resources of PUCCH reserved in accordance with the numberof CCs and contents of CSI. The configurations of a terminal and a basestation according to the present embodiment are the same as those shownin FIG. 1 and FIG. 2 used for description of Embodiment 1. The presentembodiment is different from Embodiment 1 in operation of controlchannel formation section 109 of terminal 100.

Hereinafter, a control channel formation method of terminal 100according to the present embodiment will be described. FIG. 7illustrates an example of the present embodiment when the number of CCsis 2 or less. FIG. 8 illustrates an example of the present embodimentwhen the number of CCs is 3 or more. In FIG. 7 and FIG. 8, white regionsrepresent resources reserved but not used. A/N represents ACK/NACK. Inthe following description, CSI in which only RI is included is describedas “RI” and CSI in which at least one of CQI and PMI is included isdescribed as “CQI/PMI.”

When the number of CCs is 2 or less, the present embodiment uses format2 for both when singly transmitting RI and when simultaneouslytransmitting RI and ACK/NACK, and when the number of CCs is 3 or more,the present embodiment uses format 3 for both when singly transmittingRI and when simultaneously transmitting RI and ACK/NACK. Format 3 isused irrespective of the number of CCs for both when singly transmittingCQI/PMI and when simultaneously transmitting CQI/PMI and ACK/NACK.Format 1 b is used when ACK/NACK is singly transmitted if the number ofCCs is 2 or less and format 3 is used if the number of CCs is 3 or more.

For this reason, as shown in FIG. 7, when the number of CCs is 2 orless, terminal 100 always (in every subframe) reserves format 1 bresources, reserves format 2 resources at timing of transmitting RI andreserves format 3 resources at timing of transmitting CQI/PMI. As shownin FIG. 8, when the number of CCs is 3 or more, terminal 100 always (inevery subframe) reserves format 3 resources.

In the present embodiment, when the number of CCs is 2 or less, terminal100 need not reserve format 3 at transmission timing of RI and terminal100 need not reserve format 2 at transmission timing of CQI/PMI, and itis thereby possible to reduce waste of resources compared to the relatedart. Since neither RI nor ACK/NACK has many bits (on the order of amaximum of 6 bits), if the number of CCs is 2 or less, when RI andACK/NACK are simultaneously transmitted, it is possible to achieve asufficiently low error rate even when using format 2 resources. Sincephysical resources (band, code or time resources) required fortransmission of format 2 are fewer than resources required fortransmission of format 3, using format 2 for simultaneous transmissionof RI and ACK/NACK can reduce resources required for transmission.

In the present embodiment as well as Embodiment 1, when the number ofCCs is 3 or more, terminal 100 need not reserve format 2 at transmissiontiming of CSI, and can thereby reduce waste of resources compared to therelated art.

In the present embodiment, when RI and ACK/NACK are simultaneouslygenerated, RI may be dropped (not transmitted) without simultaneouslytransmitting RI and ACK/NACK. Thus, terminal 100 need not performmultiplexed transmission processing on RI and ACK/NACK in format 2. Inthis case, base station 200 may assign downlink data so that RI andACK/NACK are not simultaneously generated. Since the transmission cycleof RI is relatively long, substantial constraints of downlink dataassignment are small and the influence on the downlink throughput issmall.

A bit string obtained by combining RI and ACK/NACK may be subjected tothe same coding (joint coding) and CQI, PMI and ACK/NACK may besubjected to different types of coding (e.g., RM coding) (separatecoding). Generally, ACK/NACK rather than CQI or PMI has a lower requirederror rate, and it is thereby possible to increase coding rates of CQIand PMI and decrease a coding rate of ACK/NACK and encode themseparately, and thereby perform transmission that satisfies requirederror rates efficiently. On the other hand, RI has a required error rateon the same level as that of ACK/NACK, and so performing the same codingallows more bits to be encoded, which improves coding performance andreduce the error rate.

The number of bits of RI differs depending on the number of transmittingantennas (or the maximum number of transmission layers), and the greaterthe maximum number of transmission layers, the greater the number ofbits becomes. Thus, transmission in format 3 may be adopted when thenumber of bits of RI is greater than a predetermined value andtransmission in format 2 may be adopted when the number of bits of RI isequal to or less than the predetermined value.

Embodiment 3

The transmission format of PUCCH used for transmission of ACK/NACK orresources to be used varies depending on the number of CCs. Thus, whenan RRC configuration is changed, for example, when SCell is added,fallback operation is performed. In the fallback operation, whendownlink data is assigned by only PCC, the same operation as that of theprevious release (e.g., Rel.8) is performed. That is, the terminaltransmits ACK/NACK in format 1 a/1 b. By carrying out fallbackoperation, the terminal can communicate with the base station even foran indeterminate period from start to completion of a change in the RRCconfiguration (period during which recognition of ACK/NACK resources maydiffer between the base station and the terminal. That is, the terminalassigns ACK/NACK to only PCC during an indeterminate period, and therebyallows recognition of ACK/NACK resources to match with that of the basestation.

In Embodiment 3, a control channel formation method during fallbackoperation will be described. The configurations of a terminal and a basestation according to the present embodiment are the same as those shownin FIG. 1 and FIG. 2 used to describe Embodiment 1. The presentembodiment is different from Embodiment 1 in operation of controlchannel formation section 109 of terminal 100.

FIG. 9 illustrates an example of the present embodiment when the numberof CCs is 2 or less. FIG. 10 illustrates an example of the presentembodiment when the number of CCs is 3 or more. In FIG. 9 and FIG. 10,white regions represent resources reserved but not used. A/N1 isACK/NACK intended for PCC, and A/N2 and A/N3 are ACK/NACKs intended forSCC.

As shown in FIG. 9 and FIG. 10, when singly transmitting ACK/NACKintended for PCC, the present embodiment performs a fallback operationto Rel.8 (or Rel.10) regardless of the number of CCs, and thus usesformat 1 a/1 b which is the same resource as that in Rel.8. On the otherhand, when simultaneously transmitting ACK/NACK intended for PCC andCSI, the present embodiment uses format 3.

That is, the present embodiment performs a fallback operation insubframes in which CSI is not transmitted and performs no fallbackoperation in subframes in which CSI is transmitted.

As described above, in the present embodiment, terminal 100 performs afallback operation only in subframes in which CSI is not transmitted,and can thereby support simultaneous transmission of ACK/NACK and CSIwhile securing communication with the base station during anindeterminate period. In addition, the base station assigns data tosubframes other than subframes in which CSI is transmitted, and therebyallows recognition of ACK/NACK resources to match with that of terminal100. That is, in the present embodiment, with attention focused on thefact that CSI is periodically (that is, discontinuously) transmitted,terminal 100 performs a fallback operation only in subframes in whichCSI is not transmitted, and can thereby simultaneously transmit ACK/NACKand CSI while securing communication during an indeterminate periodafter a configuration change. In this case, the base station assignsdata to subframes other than subframes in which CSI is transmitted,thereby allowing the base station and terminal 100 to carry outcommunication with matched recognition of ACK/NACK resources.

Embodiment 4

The base station indicates, to terminal 100, resources to be used fortransmission of ACK/NACK intended for SCC using an ARI (ACK/NACKResource Indicator) field of PDCCH (Physical Uplink Control Channel)whereby assignment of downlink data for SCC is indicated. In this case,the base station indicates one resource selected from among fourresources configured beforehand for each terminal using 2 bits in PDCCH(hereinafter, this resource is described as “indication resource”).

Embodiment 4 will describe a control channel formation method in a casewhere when the number of CCs is 3 or more, that is, when ACK/NACK istransmitted using format 3 resources, ACK/NACK including ACK/NACKintended for SCC, and CSI are simultaneously transmitted.

The configurations of a terminal and a base station according to thepresent embodiment are the same as those shown in FIG. 1 and FIG. 2 usedto describe Embodiment 1. The present embodiment is different fromEmbodiment 1 in operation of control channel formation section 109 ofterminal 100.

FIG. 11 illustrates an example of the present embodiment when the numberof CCs is 3 or more. In FIG. 11, A/N1 represents ACK/NACK for PCC, andA/N2 and A/N3 represent ACK/NACKs for SCC.

As shown in FIG. 11, in subframes in which CSI is not transmitted,terminal 100 forms control channels using indication resources(operation of Rel.10). On the other hand, in subframes in which CSI istransmitted, terminal 100 configures one resource (format 3) fortransmitting CSI beforehand (hereinafter, this resource will bedescribed as “configuration resource”). When singly transmitting CSI orwhen simultaneously transmitting ACK/NACK including ACK/NACK intendedfor PCC, and CSI, terminal 100 forms control channels usingconfiguration resources. When simultaneously transmitting ACK/NACKincluding ACK/NACK for SCC, and CSI, terminal 100 forms control channelsusing one of two methods which will be described below.

(Method 1)

Terminal 100 forms control channels for transmitting control informationmade up of ACK/NACK including ACK/NACK intended for SCC, and CSI usingconfiguration resources. That is, terminal 100 uses configurationresources regardless of whether there is downlink data assignmentintended for SCC or not.

(Method 2)

Terminal 100 forms control channels for transmitting control informationmade up of ACK/NACK including ACK/NACK for SCC, and CSI using indicationresources. That is, terminal 100 uses configuration resources when thereis no downlink data assignment intended for SCC and uses indicationresources when there is downlink data assignment intended for SCC.

In the case of method 1, since resources for transmitting ACK/NACK andCSI even when PDCCH to which SCC downlink data is assigned cannot bereceived (reception error) are not different from resources when PDCCHof SCC is successfully received, it is possible to avoid any mismatch inrecognition of ACK/NACK resources between the base station and terminal100. Therefore, the base station need not perform blind detection suchas power determination on resources whereby ACK/NACK is transmitted, andcan thereby adopt a simpler configuration.

In the case of method 2, since resources when there is ACK/NACK intendedfor SCC are different from resources when there is no ACK/NACK intendedfor SCC, base station 200 performs blind detection such as powerdetermination, and can thereby detect whether or not there is anyreception error of PDCCH of SCC in terminal 100, that is, make a DTXdetection. For this reason, base station 200 can correctly recognize areception situation of data intended for SCC in terminal 100, performretransmission with appropriate RV (Redundancy version) in HARQ(Hybrid-Automatic Request), and thereby improve an error rate orthroughput. However, since it is necessary to reserve five resourcesbeforehand, this case is suitable for use when there is a sufficientmargin in resources such as a cell with fewer users.

In above-described methods 1 and 2, indication resources can bedesignated as resources to be configured for CSI. FIG. 12 illustrates aconfiguration example in this case. In the example in FIG. 12, one offour resources intended for ACK/NACK configured for each terminalbeforehand is designated as a resource to be configured for CSI. Thefour resources configured for each terminal are shared by eightterminals. That is, four common resources are configured in terminals(UE) 1 to 8. Transmission timings of CSI are configured to be differentfrom each other and one resource intended for CSI is configured to bethe same resource as one of ACK/NACK resources at each timing. Here, thebase station activates SCC for each terminal when large capacitytransmission data is generated and performs data transmission using bothPCC and SCC. When there is no transmission data or the amount of data issmall, the terminal de-activates SCC to suppress power consumption ofthe terminal. The terminal transmits CSI only when SCC is activated. Theabove-described resource configuration method is effective for aconfiguration of CSI resources intended for SCC. For example, when SCCof UE1 is activated (that is, data transmission for SCC is intended), itis possible to use resources to be used for ACK/NACK intended for UE1for CSI (and CSI+ACK/NACK) and the three remaining resources may beshared with other UEs. When SCC of UE1 is de-activated, UE1 does nottransmit CSI and ACK/NACK intended for SCC. For this reason, CSIresources intended for UE1 can be used for transmission of ACK/NACK ofother terminals. The same can be said to be applicable to CSI resourcesintended for PCC by associating activation/de-activation with thereception period (on-duration) of a DRX (intermittent reception)operation and non-reception period (DRX period).

This makes it possible to reduce the resource amount to be reservedwithout reducing the number of terminals to which the resources can beallocated.

The embodiments of the present invention have been described so far.

When the present invention is applied to a TDD (Time Division Duplex)system, a terminal configured with PUCCH format 3 performs the followingoperation. That is, when transmitting ACK/NACK intended for one subframeof PCC, the terminal performs fallback to format 1 a/1 b. If there areACK/NACKs in a plurality of subframes (ARI present) although they areonly for PCC, the terminal uses format 3. When transmitting dynamicallyscheduled ACK/NACKs intended for one subframe of PCC and ACK/NACKsintended for SPS, the terminal performs fallback to a channel selectionof Rel.10. In other cases, the terminal uses format 3. A terminal thatsupports ACK/NACK of 5 bits or more irrespective of the number of CCstransmits ACK/NACK using format 3. However, in subframes in which CSI istransmitted, the terminal simultaneously transmits CSI and ACK/NACKusing format 3.

Although a case has been described in the above-described embodimentswhere OFDM is used for downlink and DFT-S-OFDM is used for uplink, thepresent invention is not limited to this, but is also applicable toother transmission schemes.

Although a case has been described in the above-described embodimentswhere CSI and ACK/NACK are simultaneously transmitted using format 3 ofPUCCH, the present invention is also applicable to a case where CSI andACK/NACK are simultaneously transmitted using other physical channelssuch as PUSCH.

In each embodiment described above, the present invention is configuredusing hardware by way of example, but the invention may also be providedby software in concert with hardware.

In addition, the functional blocks used in the descriptions of theembodiments are typically implemented as LSI devices, which areintegrated circuits. The functional blocks may be formed as individualchips, or a part or all of the functional blocks may be integrated intoa single chip. The term “LSI” is used herein, but the terms “IC,”“system LSI,” “super LSI” or “ultra LSI” may be used as well dependingon the level of integration.

In addition, the circuit integration is not limited to LSI and may beachieved by dedicated circuitry or a general-purpose processor otherthan an LSI. After fabrication of LSI, a field programmable gate array(FPGA), which is programmable, or a reconfigurable processor whichallows reconfiguration of connections and settings of circuit cells inLSI may be used.

Should a circuit integration technology replacing LSI appear as a resultof advancements in semiconductor technology or other technologiesderived from the technology, the functional blocks could be integratedusing such a technology. Another possibility is the application ofbiotechnology, for example.

The disclosure of the specification, drawings, and abstract included inJapanese Patent Application No. 2012-053388 filed on Mar. 9, 2012 isincorporated herein by reference in its entirety.

The present invention is useful in mobile communication systems thatcontrol the transmission timing of uplink subframes for each CC.

REFERENCE SIGNS LIST

100 Terminal

101 Receiving section

102 FFT section

103 Demodulation section

104 Decoding section

105 Channel quality measuring section

106 ACK/NACK generating section

107 CSI generating section

108 Multiplexing section

109 Control channel formation section

110 DFT-S-OFDM signal generating section

111 Transmitting section

200 Base station

201 Receiving section

202 FFT section

203 Control channel extraction section

204 ACK/NACK demodulation section

205 CSI decoding section

206 Scheduling section

207 Coding section

208 Modulation section

209 Mapping section

210 IFFT section

211 Transmitting section

1. A communication apparatus comprising: a receiver, which, inoperation, receives, from a terminal, a control channel that is formedusing a selected one of a plurality of PUCCH (Physical Uplink ControlChannel) formats including a first PUCCH format and a second PUCCHformat, and that includes control information for one or more of aplurality of component carriers, the plurality of component carriersincluding a Primary Component Carrier (PCC) and a Secondary ComponentCarrier (SCC); and a transmitter, which, in operation, transmits, to theterminal, data based on the control information, wherein when thecontrol information includes only Channel State Information (C SI) forthe plurality of component carriers out of ACK/NACK and the CSI, thefirst PUCCH format is selected and used to form the control channel;when the control information includes the ACK/NACK and the CSI for theplurality of component carriers, the first PUCCH format is selected andused to form the control channel; when the control information includesonly the ACK/NACK out of the ACK/NACK and the CSI, the second PUCCHformat, different from the first PUCCH format, is selected and used toform the control channel; when the control information includes theACK/NACK for the SCC and the CSI, and there is no downlink dataassignment for the SCC, the control channel is formed using a resourceconfigured beforehand; and when the control information includes theACK/NACK for the SCC and the CSI and there is downlink data assignmentfor the SCC, the control channel is formed using a resource indicatedfrom the communication apparatus.
 2. The communication apparatusaccording to claim 1, wherein, when the control information includesonly ACK/NACK for three or more component carriers of the plurality ofcomponent carriers out of the ACK/NACK and the CSI, the first PUCCHformat is selected and used to form the control channel.
 3. Thecommunication apparatus according to claim 1, wherein the plurality ofPUCCH formats include a third PUCCH format, and when the controlinformation includes ACK/NACK for one or two of the plurality ofcomponent carriers and the CSI, and the CSI includes only a RankIndicator (RI) out of CQI (Channel Quality Indicator), PMI (PrecodingMatrix Indicator) and the RI, the third PUCCH format is selected andused to form the control channel.
 4. The communication apparatusaccording to claim 1, wherein when the control information includes onlythe ACK/NACK for the PCC out of the ACK/NACK and the CSI, the secondPUCCH format is selected and used to form the control channel.
 5. Thecommunication apparatus according to claim 1, wherein, when the controlinformation includes only the CSI out of the ACK/NACK and the CSI andwhen the control information includes the ACK/NACK for the PCC and theCSI, the control channel is formed using a resource configuredbeforehand.
 6. The communication apparatus according to claim 1, whereinthe resource configured for the CSI is set to be the resource indicatedfrom the communication apparatus.
 7. A communication method comprising:receiving, from a terminal, a control channel that is formed using aselected one of a plurality of PUCCH (Physical Uplink Control Channel)formats including a first PUCCH format and a second PUCCH format, andthat includes control information for one or more of a plurality ofcomponent carriers, the plurality of component carriers including aPrimary Component Carrier (PCC) and a Secondary Component Carrier (SCC);and transmitting, from a base station to the terminal, data based on thecontrol information, wherein when the control information includes onlyChannel State Information (C SI) for the plurality of component carriersout of ACK/NACK and the CSI, the first PUCCH format is selected and usedto form the control channel; when the control information includes theACK/NACK and the CSI for the plurality of component carriers, the firstPUCCH format is selected and used to form the control channel; when thecontrol information includes only the ACK/NACK out of the ACK/NACK andthe CSI, the second PUCCH format, different from the first PUCCH format,is selected and used to form the control channel; when the controlinformation includes the ACK/NACK for the SCC and the CSI, and there isno downlink data assignment for the SCC, the control channel is formedusing a resource configured beforehand; and when the control informationincludes the ACK/NACK for the SCC and the CSI and there is downlink dataassignment for the SCC, the control channel is formed using a resourceindicated from the base station.
 8. The communication method accordingto claim 7, wherein, when the control information includes only ACK/NACKfor three or more component carriers of the plurality of componentcarriers out of the ACK/NACK and the CSI, the first PUCCH format isselected and used to form the control channel.
 9. The communicationmethod according to claim 7, wherein the plurality of PUCCH formatsinclude a third PUCCH format, and when the control information includesACK/NACK for one or two of the plurality of component carriers and theCSI, and the CSI includes only a Rank Indicator (RI) out of CQI (ChannelQuality Indicator), PMI (Precoding Matrix Indicator) and the RI, thethird PUCCH format is selected and used to form the control channel. 10.The communication method according to claim 7, wherein when the controlinformation includes only the ACK/NACK for the PCC out of the ACK/NACKand the CSI, the second PUCCH format is selected and used to form thecontrol channel.
 11. The communication method according to claim 7,wherein, when the control information includes only the CSI out of theACK/NACK and the CSI and when the control information includes theACK/NACK for the PCC and the CSI, the control channel is formed using aresource configured beforehand.
 12. The communication method accordingto claim 7, wherein the resource configured for the CSI is set to be theresource indicated from the base station.